1. Field of the Invention
This invention relates to a light emitting device, an area light source apparatus and an image display apparatus.
2. Description of the Related Art
An illumination apparatus is available which illuminates using a plurality of light emitting devices each having a light emitting diode as a light source.
An illumination apparatus of the type described is used, for example, as an illuminator wherein the light source is utilized for direct illumination or is used in an image display apparatus such as a television receiver wherein the light source is used for backlight illumination.
In an image display apparatus such as a television receiver, a plurality of light emitting devices are disposed in a matrix, and light as backlight is emitted from the light emitting devices toward a display panel.
In the image display apparatus, when light is emitted from the light emitting devices, it is necessary to keep the uniformity in luminance over an overall area of the display panel. A light emitting device in the related art is disclosed in Japanese Patent No. 3,875,247 (hereinafter referred to as Patent Document 1) wherein, in order to assure the uniformity in luminance, light emitted from a light source is passed through a lens such that it is emitted so as to expand laterally from the lens and is irradiated upon the display panel.
Incidentally, in recent years, there is a tendency to reduce the thickness of an image display apparatus such as a television receiver. If it is tried to reduce the thickness of a light emitting device having the configuration of the light emitting device disclosed in Patent Document 1, then since the display panel is positioned nearer to the light emitting device, there is the possibility that the luminance of light emitted from a light emitting diode on the display panel on the front face side may become comparatively high, resulting in degradation of the uniformity in luminance over the overall area of the display panel.
Therefore, in order to increase the light emission amount to sideward directions to assure the uniformity in luminance, a light emitting device a has been proposed which uses a lens having such a shape as seen in FIG. 16. Referring to FIG. 16, the light emitting device a shown includes a light emitting diode b sealed in a sealing resin member c, and a lens d is disposed on the sealing resin member c. The lens d has a projecting portion e provided thereon such that it is positioned outwardly of the sealing resin member c and projects laterally. The lens d has an outer face f formed as a curved face and a bottom face g formed as a flat face.
If light is emitted from the light emitting diode b of the light emitting device a, then it goes out through the lens d while it is partly reflected inwardly by the outer face f of the lens d and then reflected inwardly by the bottom face g again, whereafter it goes out from the outer face f. In this manner, in the light emitting device a, since the light reflected inwardly by the outer face f and then reflected inwardly by the bottom face g again goes out from the projecting portion e positioned on the outer side with respect to the sealing resin member c, the light emitting amount toward lateral directions increases.